F-Machine Tremblr Spare Receiver Sleeve Silicone Black MReplacement silicone sleeve for the F Machine Tremblr sex machine. Made from high quality silicone using the latest molding technology available. This means you can look forward to extra performance! This silicone sleeve replaces the old latex design and can easily be used to replace the original latex sleeve. Also new is the ribbed texture, which allows the lubricant to be retained for a longer period of time, reducing the need for refills.